Low pressure fluid storage technique for a high pressure application

ABSTRACT

A technique for pre-storing an application fluid in coiled tubing for use in a downhole application. The technique includes filling the coiled tubing with the application fluid in a manner that utilizes pressures substantially below that of the pressures utilized in the downhole application itself. The coiled tubing may then be charged to near the application pressure and placed in hydraulic communication with a well for the downhole application. Thus, the coiled tubing may serve as an application fluid storage device without the requirement of coiled tubing deployment or associated equipment and related costs.

BACKGROUND

Exploring, drilling and completing hydrocarbon and other wells aregenerally complicated, time consuming and ultimately very expensiveendeavors. As a result, oilfield efforts are often largely focused ontechniques for maximizing recovery from each and every well. Whether thefocus is on drilling, unique architecture, or step by step interventionsdirected at well fracturing or stimulation, the techniques have becomequite developed over the years. One such operation at the well sitedirected at enhancing hydrocarbon recovery from the well is referred toas a stimulation application. Generally, in conjunction with fracturing,a stimulation application is one in which a large amount of proppant,often a type of sand, is directed downhole at high pressure in the formof a fluid slurry. So, for example, downhole well perforations into aformation adjacent the well which have been formed by fracturing may befurther opened and/or reinforced for sake of recovery therefrom.

In order to help ensure that the proppant containing slurry is able toreach all well perforations, for sake of reinforcement as noted above, adiverter application may be run. A diverter application is another highpressure application in which a chemical diverter material slurry isintroduced to the well prior to the introduction of the proppant so asto help ensure that access to all perforation locations by the proppantis available.

For effectiveness, slurries such as those described above are oftensupplied downhole at considerable rates and pressures. For example, itwould not be uncommon for slurries to be pumped at more than 60 or 100barrels per minute (BPM) at pressures exceeding 10,000 PSI. Thus, inorder to ensure that a sufficient volume, rate and pressure of theslurry is delivered during the applications, a host of positivedisplacement pumps are often positioned at the oilfield for sake ofdriving the applications. Specifically, each one of several pumps may befluidly linked to a manifold which coordinates the overall delivery ofthe slurry fluid downhole.

Each of the noted positive displacement pumps may include a plungerdriven by a crankshaft toward and away from a chamber in order todramatically effect a high or low pressure on the chamber. This makes ita good choice for high pressure applications. Indeed, even outside ofstimulation operations, where fluid pressure exceeding a few thousandpounds per square inch (PSI) is to be generated, a positive displacementpump is generally employed. In the case of stimulation operationsspecifically though, this manner of operation is used to effectivelydirect an abrasive containing fluid through a well.

As is often the case with large systems and industrial equipment,regular monitoring and maintenance of positive displacement pumps may besought to help ensure uptime and increase efficiency. In the case ofhydraulic fracturing applications, a pump may be employed at a well andoperated for an extended period of time, say six to twelve hours per dayfor more than a week. Over this time, the pump may be susceptible towearing components such as the development of internal valve leaks. Thisis particularly of concern at conformable valve inserts used at theinterface of the valve and valve seat. These “inserts” are elastomericseals that are located in relatively challenging internal pump locationsand must be manually inspected. Generally, due to the minimal costsinvolved, regardless of whether the inspection reveals defects, theseals will be replaced once the scheduled inspection has begun.

However, perhaps of greater concern regarding such valves, is thesusceptibility to clogging. For example, even though pumping a proppantmay wear on seals, it is unlikely to lead to clogging of valves withinthe pump due to the minimal sizes of the proppant particles that aregenerally utilized. However, as noted above, other applications, such asa diverter application or flowback prevention efforts may use largerfiber particles or beads. More specifically, it would not be uncommon tosee fibers in excess of 4-5 mm in length utilized in such applications(or similarly sized flakes or rods). However, the architecture of apositive displacement pump is tailored to maximizing and maintainingpressure. So, for example, under current architectural protocol, theclearance space at valves within such pumps is generally no more thanabout 4 mm. Thus, unfortunately, when pumping a slurry utilizingconstituents in excess of 4 mm, a high probability of clogging at thevalves within the pump may result. Furthermore, a host of otherapplications driven by a positive displacement pump may utilizeconstituents exceeding 4 mm, such as ball launching applications andothers.

The hazards of a clogged valve may be quite dramatic. For example, aplunger of a clogged positive displacement pump may continuereciprocating and driving up pressure within the pump which can lead toa blowout. This may consist of a pres sure-based explosion of a fittingor other connection to the pump resulting in operator injury at theoilfield.

Efforts have been undertaken to avoid running large particle slurriesthrough high pressure pumps. For example, a storage manifold containingthe slurry may be pressurized to near the level of an adjunct highpressure pump and connected to the pump at its high pressure side. Thus,the manifold's contents may be pumped out of storage and toward the wellby a fluid that does not include such large particles. In this manner,the large particle slurry never actually goes through the pump andvalves thereof. However, this type of “injecting” of the large particlecontaining slurry is only practical in limited volumes. That is, wherean application calls for 25-100 barrels or more of slurry, it would notbe practical to load and place a conventional pressurizable tankadjacent to the pump. This would be the equivalent of placing anenormous pressurized tank with seams and other weakpoints at thewellsite. The measures required to ensure safety of such a tank would beimpractical in terms of required wall thicknesses, seam reinforcementand overall expense.

SUMMARY

A method of delivering fluid to a downhole location in a well for anapplication therein. The method includes pumping the fluid into coiledtubing that is positioned at an oilfield surface adjacent the well. Thispumping of the fluid into the coiled tubing takes place at a fillingpressure. The fluid may subsequently be transferred from the coiledtubing to the downhole location at an application pressure that isgreater than the filling pressure. Additionally, pressure in the coiledtubing may be increased from the filling pressure to a pre-applicationpressure that is closer to the application pressure than the fillingpressure prior to the transferring of the fluid downhole.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an embodiment of a pre-application storagesystem including coiled tubing storage equipment accommodating high andlow pressure lines.

FIG. 2A is a side cross-sectional view of an embodiment of a highpressure pump of the pre-application storage system of FIG. 1.

FIG. 2B is a side cross-sectional view of the coiled tubing equipment ofFIG. 1 filled with an application fluid.

FIG. 3 is a side view of the coiled tubing equipment of FIG. 1 revealinghookup detail on the high and low pressure lines thereto.

FIG. 4 is a schematic overview of an embodiment of the pre-applicationstorage system of FIG. 1 positioned at an oilfield for use in a highpressure application.

FIG. 5 is a side cross-sectional view of a well at the oilfield of FIG.4 upon running the high pressure application supported by thepre-application storage system.

FIG. 6 is a flow-chart summarizing an embodiment of utilizing apre-application storage system to support a high pressure application ina well.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providean understanding of the present disclosure. However, it will beunderstood by those skilled in the art that the embodiments describedmay be practiced without these particular details. Further, numerousvariations or modifications may be employed which remain contemplated bythe embodiments as specifically described.

Embodiments are described with reference to certain embodiments ofoilfield operations. Specifically, stimulation operations involvingfracturing or stimulating of a well are detailed herein. Theseoperations may include the introduction of slurries containing chemicaldiverter materials, flowback inhibiting fibers and other sizableparticles that often present challenges to pumping at high pressures forstimulation operations. However, other types of oilfield operations maybenefit from the pre-application storage techniques detailed herein. Forexample, storing a sizable amount of application fluid at the wellsitein readily available coiled tubing that is uniquely brought on-line maybe of benefit for any number of applications regardless of fluidparticle sizes involved. Indeed, so long as coiled tubing is filled withan application fluid at an initial pressure and then utilized to deliverthe application fluid at an application pressure above the initialpressure, appreciable benefit may be realized.

Referring specifically now to FIG. 1, a side view of an embodiment of apre-application storage system 101 is shown. In this embodiment, coiledtubing storage equipment 100 is utilized to accommodate an applicationfluid such as a stimulation-related slurry in advance of being used in adownhole application in a well. That is, as opposed to running theslurry through a high pressure application pump 175 such as the onedepicted, the slurry is first delivered and stored in coiled tubing 110by another less pressurized means. The fluid may then later be pumpedfrom the tubing 100 by utilizing the application pump 175 of the system101. Specifically, the application pump 175 may pump a driving fluidtoward the coiled tubing 110 to send the slurry therefrom at anappropriate application pressure. Thus, as depicted, the coiled tubingequipment 100 includes hookups for connections to both a high pressureline 125 for fluid coupling to the application pump 175 as well as a lowpressure line 150 for fluid coupling to a source for obtaining theslurry during filling.

Pre-storing the application slurry in coiled tubing 110 means that theslurry does not need to be routed through the application pump 175 inorder to be utilized in a downhole application. This may be particularlyadvantageous where the slurry contains particles that are sizeableenough to potentially clog or obstruct valves within the applicationpump 175. For example, in the embodiment shown, the application pump 175is a conventional triplex pump of a type that is commonly utilized atoilfield worksites. The pump 175 is coupled to an engine 160 that powersa sizable crankshaft 140 to drive internal plungers toward and away fromvalves that regulate flow and pressure of fluid through the pump 175. Inthis way, pressure of the fluid may be dramatically driven up, forexample, to in excess of 10,000 or in excess of 15,000 PSI if need befor an oilfield application. While this makes such pumps 175 a goodoption for certain oilfield applications that require such pressure, asdescribed further below, the valves are generally of limited clearance,often below about 5 mm, in order to ensure such pressures. However, inan embodiment as shown, where the coiled tubing 110 is utilized topre-store the slurry, the limited clearance afforded by the valves ofthe pump 175 has no bearing on particle sizes utilized in the slurry.Thus, if the optimal slurry for the application at hand involves the useof fibers or particles exceeding 4-5 mm, or a large volume of similarlysized balls, flakes, rods, etc., the limited clearance of the valves inthe pump 175 are not at issue. The slurry is already filled in thecoiled tubing 110.

Since the pump used to fill the coiled tubing 110 need not be utilizedfor actually running the downhole application with the slurry, it alsodoes not need to provide higher application pressures like theapplication pump 175. Therefore, it does not face the valve clearancelimitations faced by the application pump 175. Instead, with addedreference to FIG. 4, slurry supply equipment 450 may include a slurrytank and pump assembly where a conventional transfer pump directs theslurry to the coiled tubing 110 through the low pressure line 150 atless than about 200 or less than about 500 PSI. That is, enough pressureto achieve loading of the coiled tubing 110 with the slurry issufficient. For example, a c-pump or other fan-type pump may beutilized. Thus, valve clearances and other constraints are not at issue.

Continuing with reference to FIG. 1, the depicted system 101 utilizesgenerally known oilfield equipment. For example, as noted theapplication pump 175 and associated machinery may be provided as part ofa standard mobile pump truck 145 (also see FIG. 4). Further, the outletpipe 180 for providing the high pressure fluid, which ultimatelysupports the driving of the slurry, is routed to a manifold 190 wherethe noted high pressure line 125 delivers the driving fluid to commoncoiled tubing 110. However, it is worth noting that the high pressure,larger slurry constituent type applications suggested here are nottraditional coiled tubing applications. Thus, it is likely that but forbeing deliberately brought on sight for sake of slurry storage, nocoiled tubing would be available. Indeed, even in the depictedembodiment, the coiled tubing 110 is not provided to support directcoiled tubing delivery of the slurry. Thus, the expense of providing andmaintaining an injector and other large equipment such as a crane ormast unit, mixing equipment, etc. to support such deployment need not beundertaken in the depicted embodiment. Instead, the coiled tubing 110alone is deliberately brought on site as a unique non-interventionalslurry storage device with advantages over conventional pressurizablestorage tanks or vessels as detailed further below.

As also detailed further below, in one embodiment the coiled tubing 110may be coiled tubing that was previously considered “retired”. That is,for traditional coiled tubing use, there is an estimated “coil life” interms of the number of deployments into a well and recoiling beforerepeated plastic deformation, cracking and other wear is considered suchthat the coiled tubing 110 should be retired. So, for example, dependingon materials, construction, wall thickness and other tolerance factors,a given coiled tubing 110 may be assigned a “coil life” of 50deployments and scheduled for retirement upon reaching 90% of thisexpected life (e.g. after 45 deployments). Of course, other retirementguidelines may be applied. For example, retirement may be scheduled totake place once the coiled tubing reaches anywhere between about 75% and95% of coil life. Regardless, while such coiled tubing 110 may no longerbe ideal for further deployments, it may be perfectly sufficient for useas a unique slurry storage device as detailed herein. Thus, as opposedto discarding the potentially several hundred thousand dollar coiledtubing 110, it may be reliably repurposed after the “coil life” to anext “storage life” of potentially indefinite duration. Further, this“repurposing” does not require substantial added labor or equipment costto attain other than the time required to reclassify and keep track ofthe coiled tubing 110 going forward.

In other circumstances, the coiled tubing 110 may be retired for otherreasons. For example, coiled tubing 110 may be trimmed after repeateduses resulting in a coiled tubing that is no longer practically usablefor available interventions. Nevertheless, this shorter coiled tubing110 may provide more than adequate volume for sake of storingapplication fluid 215 as detailed herein (see FIG. 2).

As a storage device, the coiled tubing 110 can readily hold in excess of30 or in excess of 60 or in excess of 100 or in excess of 150 or inexcess of 200 or in excess of 300 or in excess of 400 hundred barrels ofslurry or other fluid, need not be subjected to further deployment andplastic deformation and is even compactly wound in such a manner as tobe self-reinforcing. Indeed, in the embodiment shown, in addition to theretaining sidewalls 107 of the equipment reel, containment bars 105 mayalso optionally be provided across the outer portion of the reel. Thisprovides added support to the outermost exposed portions of coiledtubing 110, particularly once pressurized and does not present anobstacle to utilizing the coiled tubing 110 as a storage device (i.e. inthe general circumstance where the tubing 110 is not intended to bedeployed).

Referring now to FIG. 2A, a side cross-sectional view of an embodimentof the high pressure application pump 175 of FIG. 1 is shown. In thisview, the driving fluid 200 that is circulated through the pump 175which is ultimately directed at the coiled tubing 110 of FIG. 1, doesnot contain particles, fibers or other materials prone to occluding theinternal valves 270, 255. With added reference to FIG. 2B, suchmaterials (e.g. 240) may be called for in the applications slurry 215that is stored in the coiled tubing 110. However, the driving fluid 200through the pump 175 need not serve as a downhole application fluid.Thus, it is free to be tailored with viscosity and other characteristicssuited to advance pressure and drive the application fluid 215 withoutthe requirement of including large application fluid particles itself.

As noted above, the plunger 225 of the pump 175 is stroked toward andaway from a chamber 205 to draw in and then drive up fluid pressuretherein. That is, as the plunger 225 moves away from the chamber 205,the pressure in the chamber decreases to a predetermined point thatlifts the lower valve 255 drawing in the driving fluid 200. Then, as theplunger 225 moves toward the chamber 205, pressure in the chamber 205increases until the upper valve 270 is forced open. In this manner, thedriving fluid 200 is pressurized and ultimately circulated out of thepump 175 (e.g. toward the coiled tubing 110 and application fluid 215 asshown in FIG. 2B). As noted above, in spite of the potentially limitedclearance between an open valve 270 and seat 275, the driving fluid 200does not serve as the application fluid 215 and need not includepotentially large occlusive particles which may be found in theapplication fluid 215 (again, see FIG. 2B).

Referring now to FIG. 2B, a side cross-sectional view of the coiledtubing 110 of FIG. 1 is shown that reveals the application fluid 215therein. As with any coiled tubing 110, the structure is defined by acontinuous tubular wall 210 that includes only a single seam for weldingtogether. In effect, the only practical leak points for the coiledtubing 110 under standard oilfield application pressures would be theunlikely scenario of leakage from one end or another thereof. Even in acircumstance where the tubing 110 is straightened out, as opposed towrapped around itself as depicted, a reliably high pressure rating isreadily attainable. For example, even for coiled tubing 110 that isretired in terms of coil life as described above, a pressure rating of15,000 to 20,000 PSI may be reasonably expected.

As noted above, coiled tubing 110 inherently has advantages over aconventional storage tank due to the excessive wall thicknessrequirements, potential numerous seams and other tank-related drawbackswhere a substantial pressure rating is at issue. Specifically, inaddition to the singular seam that is present in coiled tubingconstruction, the dimensions are such that the surface (i.e. innersurface) to volume ratio of the coiled tubing wall 210 to the volume ofapplication fluid 215 therein is large enough to enhance the pressurerating or capacity of the structure. For example, given that standardcoiled tubing 110 is likely less than about 3 inches in diameter, thesurface to volume ratio will be at least 1.3333 per unit length ofcoiled tubing 110 (e.g. 2÷ the radius (1.5) of the coiled tubing 110).For a common 2⅜ inch diameter coiled tubing 110, which generally has aninner diameter of about 2 inches, the surface to volume ratio would goup to 2 (e.g. 2÷ the radius (1) of the coiled tubing 110).

As used herein, the term “coiled tubing” as applied for a fluid storagedevice is not necessarily meant to be limited to conventional coiledtubing that has at some point been utilized in a prior deployment for adownhole application or constructed for such operations. Just as a“retired” coiled tubing may suffice as a storage device for applicationfluid 215 as described above, so too would any tubular having a surfaceto volume ratio of at least about 1 or at least about 1.2 or at leastabout 1.3 or at least about 1.5 or at least about 2, whether or not suchis considered coiled tubing in the conventional sense.

As depicted in FIGS. 1 and 2B, as a matter of practicality anduser-friendliness, circumstances would generally dictate that the coiledtubing 110 be wrapped about itself on a reel to accommodate potentiallythousands of feet thereof. Thus, not only is the coiled tubing 110 ableto store in excess of about 30 or in excess of about of 30 or in excessof 60 or in excess of 100 or in excess of 150 or in excess of 200 or inexcess of 300 or in excess of 400 hundred barrels barrels of applicationfluid 215 at several thousand PSI, but it also displays aself-reinforcing character once pressurized.

In FIG. 2B it is apparent that upon wrapping about itself, thecontinuous wall 210 of coiled tubing 110 repeatedly overlays andcontacts itself at a variety of interfacing locations 220. Theselocations 220 appear to be isolated points in the cross-sectionaldepiction of FIG. 2B. However, the degree of reinforced interfacinggenerally continues for a distance as one stretch of coiled tubing 110abuts another in a close wrapped fashion. Further, while the coiledtubing 110 is shown almost perfectly circular for ease of illustration,a certain degree of flattening or plastic deformation is likely as theweight and stress of the coiled tubing 110 builds upon itself as itwraps about itself. Thus, the interfacing locations 220 are likely to beof a broader nature than an isolated point. As a result, the greatersurface area of the interfacing provides a greater degree ofself-reinforcement. Thus, not only is the coiled tubing 110 readily highpressure rated even in an unwrapped state, as a practical matter, awrapped “retired” coiled tubing 110 may be even more reliably safe forhigh pressure use as a high pressure fluid storage device.

Continuing with reference to FIG. 2B, the pressurized space 260 withinthe coiled tubing 110 accommodates an application slurry 215 as noted.Unlike the driving fluid 200 of FIG. 2A, there is no longer a concernover valve clearance issues. Thus, the slurry 215 may include largeconstituents 240. In the embodiment shown, these constituents exceedabout 4 mm and are fibrous in nature, such as flowback inhibiting ordiverting fibers often utilized with proppant 245 during stimulationapplications. Indeed, with a standard 2⅜ inch coiled tubing having justunder 2 inches in inner diameter to work with, balls or large divertermaterial of 1.5 inches or so may be utilized without concern over sizeissues. This is in sharp contrast to circumstances in which theapplication fluid is to be pumped through the application pump 175 ofFIG. 2A where use of constituents of such size would be impractical.

In addition to the specifically noted applications here, those in whicha slurry incorporates irregular particle shapes that may presentclearance issues may also be candidates for use with coiled tubing 110as a pre-application storage device. Further, high concentration fiberpill applications of 500 to 1,000 ppt or more may be benefically storedin coiled tubing 110 prior to application. Similarly, superconcentratedsand slurries with up to 20 lbs. of sand per gallon of clean fluid maybe pumped through the coiled tubing 110, for example to slow down theother pumps 445 or dilute the sand of the superconcentrated slurrywithout concern over damage to the application pump 175 (see FIG. 4).The same hold true for ball launcher applications, viscous pillapplications and even applications that employ materials or constituentsthat are potentially damaging to pump parts such as valve seals.

The slurry 215 of FIG. 2B includes different constituents 240, 245 thathave been mixed and supplied to the coiled tubing 110 from anotherlocation (e.g. see 450 of FIG. 4). Another added advantage of utilizingcoiled tubing 110 in place of a more unitary large volume tank-type ofstructure to serve as a storage device is the control over the mixedslurry 215. That is, the narrow geometrical fluid space 260 of less thanabout 2 inches stretched out over potentially thousands of feet, aswould be common for coiled tubing 110, discourages settling andseparation among such mixed components 240, 245. Indeed, utilizing asufficient viscosity in the base fluid in combination with coiled tubing110 as a storage device should substantially eliminate the occurrence ofsettling and/or separation.

At the same time, however, once the driving fluid 200 of FIG. 2A is usedto push the slurry 215, the area of interface between the fluids 200,215 is also limited by the coiled tubing dimensions. Thus, anycontamination of the application fluid 215 with the driving fluid 200 isalso kept to a minimum. Ultimately, this means that once the applicationfluid 215 is delivered downhole during an application as describedfurther below, it is likely to be enhanced in terms of lack ofcontamination and dilution as well as maintenance of mixed constituents240, 245.

Continuing now with reference to FIG. 3, a side view of the coiledtubing equipment 100 of FIG. 1 is shown. From this side view, hookupdetail for the high 125 and low 150 pressure lines is visible. In thisview, the retaining sidewalls 107 are not shown so as to reveal theunderlying coiled tubing 110. An inlet line 375 to the coiled tubing 110emerges from a common manifold 300 secured to the hub 340 of theequipment reel 100. The low pressure line 150 is used to allowapplication fluid 215 into the inlet 375, for example, from lowerpressure pump equipment 450 as described above (also see FIGS. 2B and4).

The low pressure line 150 also includes a loading port 325. Thus,continuing with added reference to FIG. 2B, a foam plug, viscous pill,ball, dart or other implement may be introduced to the application fluid215 through the port 325 during the filling of the coiled tubing 110therewith. For example, once the coiled tubing 110 is largely filled, aplug may be dropped into the low pressure line 150. After a moment, oncethe plug has at least reached the inlet 375, the low pressure line 150may be closed off at the manifold 300. At this point, the coiled tubing110 may simply serve as a storage device of application fluid 215 at theoilfield. However, when the time arises to deliver the application fluid215, the high pressure line 125 may be opened and driving fluid 200 usedto interface the plug and push application fluid 215 out of the coiledtubing 110 (see also FIG. 2A). While a plug may provide a barrier tominimize mixing of application 215 and driving 200 fluids, this is notnecessarily required. Indeed, a driving fluid 200 that is of greaterviscosity than the application fluid 215 may be sufficient to preventsubstantial mixing. Furthermore, given the coiled tubing 110 manner ofstorage mixing may not be of considerable concern, regardless.

Referring now to FIG. 4, a schematic overview of an embodiment of thepre-application storage system 101 of FIG. 1 is shown positioned at anoilfield 400 for use in a high pressure application. As would generallybe the case in such circumstances a central manifold 470 or “missile” isused to acquire a low pressure slurry from a mixer 465 for distributionto a host of high pressure pumps 445. These pumps 445 may be used todrive up the pressure of the slurry substantially, for example, fromless than 200 PSI to several thousand PSI, and then send the pressurizedslurry back to the missile 470. In this way the missile 470 is able todirect the pressurized slurry to a wellhead 490 over a delivery line 475for an application downhole in a well. In the embodiment shown, themixer 465 is a mobile unit that acquires fluid and other constituentsfrom adjacent tanks 467 for blending with proppant or other materialsfrom another mobile unit 460 in order to form the slurry. Regardless,for the embodiments described here, none of these constituents,proppants or other materials are of a size to present a challenge tointernal valves of the high pressure pumps 445.

Continuing with reference to FIG. 4, with added reference to FIG. 2B,the unique pre-application storage system 101 is provided forcircumstances where sizable materials are called for that may presentchallenges to internal high pressure pump valves due to clearancelimitations. More specifically, as noted above, slurry supply equipment450 may be used to direct an application fluid 215 over a low pressureline 150 to a coiled tubing storage device 100. That is, without therequirement of particularly high pressure, the application fluid 215 mayinclude large particles, lengthy fibers and other materials that mightotherwise be prone to face internal valve issues if directed through ahigh pressure pump (e.g. 445). Instead, with the coiled tubing storagedevice 100 pre-loaded with the application fluid 215, high pressure maybe supplied by an application pump 175 at a mobile pump truck 145.

In the embodiment shown, driving fluid 200 from a fluid tank 415 may bedrawn over a delivery line 430 into the application pump 175 where it ispressurized and directed over the high pressure line 125 to the coiledtubing storage device 100. In this way, the application fluid 215 may bepressurized. Pressurization of the application fluid 215 may be a matterof charging the fluid 215 for later use. For example, once apredetermined pressure is reached, a remotely actuated valve 480 may bekept closed and the fluid 215 saved for later use. In one embodiment,the predetermined pressure is approximately that of the pressureattained by the high pressure pumps 445 as applied to a slurry beingdirected at the wellhead 490 as described above. So, for example,consider an embodiment where the slurry is a proppant containing slurryfor use in a fracturing application, and the pressure to be attained bythe missile 470 is 15,000 PSI. In this situation, the correspondingpressure charge of the application fluid 215 in the coiled tubingequipment 100 may be held at between about 14,000 PSI and 16,000 PSI.

Continuing with the example scenario above, once the applicationprotocol calls for the introduction of the application fluid 215, forexample to provide large flowback inhibiting fibers to the fracturingapplication, the valve 480 may be remotely opened. In this way, theapplication fluid 215 may be added to the fracturing application withoutever subjecting high pressure pumps 445 to large fibers that mightpresent pumping issues. The pre-charging of the coiled tubing equipment100 may help to avoid any pressure differential induced shock to thesystem during the adding of the application fluid 215. Further, assuggested above, during the addition of the application fluid 215 to theprocess, the application pump 175 may operate to maintain pressure andcontinue advancement of the fluid 215. In one embodiment this mayinclude remotely opening the valve 480 and operating the pump 175 for apredetermined period in order to deliver a known quantity of theapplication fluid 215 to the system for downhole delivery.

Of course, a variety of other configurations may be employed forintroducing the pre-stored application fluid 215 to the system. Forexample, the valve 480 may be opened allowing the application fluid 215to be drawn into the delivery line 475 without any support from anapplication pump 175. This could be achieved by having the coiled tubingequipment 100 intentionally supercharged above the application pressureof the high pressure pumps 445 and/or coupling to the delivery line 475in a Venturi-like manner to allow the application fluid 215 to bleedinto the process.

Referring now to FIG. 5, a side cross-sectional view of a well 580 isshown at the oilfield 400 of FIG. 4. The well 580 extends below thewellhead 490 traversing multiple formation layers 590, 595 beforereaching perforations 575. The perforations 575 extend beyond casing 585defining the well and into the surrounding formation 595 to encouragethe production of hydrocarbons therefrom. As described above, theperforations 575 are shown accommodating flowback inhibiting fibers 240to enhance the performance of proppant directed at the perforations 575.While these fibers 240 may present challenges to being delivered bypumping through a conventional high pressure pump, for embodimentsherein, they have been provided by way of pre-storing at a coiled tubingstorage device positioned at the oilfield 400 without being run throughsuch a pump. Thus, such pumping issues are effectively eliminated.

While the example depicted in FIG. 5 illustrates the benefit ofdelivering large fibers downhole while avoiding pumping issues, avariety of other large particle materials may be delivered to the well580 in a similarly beneficial manner. For example, diversion material,cement, balls and other projectiles, and a variety of other sizablematerials may be delivered to the well 580 according to the techniquesdescribed herein.

Referring now to FIG. 6, a flow-chart is depicted which summarizes anembodiment of utilizing a pre-application storage system to support ahigh pressure application in a well. Specifically, coiled tubing isfilled with an application fluid at a filling pressure as noted at 620.This filling pressure is lower than the application pressure that islater utilized during an application with the application fluid. Withthe coiled tubing containing the application fluid, it may be stored atan oilfield location for an operator-determined period (see 635).However, at some point, the application fluid is delivered to a downholeapplication as noted at 695. This delivery takes place at a higherapplication pressure. In one embodiment, the application fluid in thecoiled tubing is pre-charged to a pre-application pressure above thefilling pressure (see 665). The application pressure is closer to thispre-application pressure than the filling pressure. In anotherembodiment, a plug is introduced to the application fluid in advance ofthe charging to the pre-application pressure so as to provide a barrierbetween the application fluid and a subsequently introduced drivingfluid (see 650). That is, as indicated at 680, with or without such abarrier, a driving fluid may be directed at high pressure to aid in thedelivering of the application fluid to the well from the coiled tubing.

Embodiments detailed hereinabove provide unique methods and equipmentsetups for running high pressure applications without running anapplication fluid through a high pressure pump. Further, these methodsand setups do not rely on the use of conventional storage manifolds orjointed piping that are subject to small volume application limits.Similarly, the methods and setups herein do not require the impracticalconstruction of potentially hazardous and expensive pressurizable tanksfor use at a worksite. Instead, generally readily available coiledtubing equipment may be uniquely reconfigured and incorporated into apre-application system for storing and delivering the application fluidin a safe, reliable and practical manner.

The preceding description has been presented with reference to presentlypreferred embodiments. Persons skilled in the art and technology towhich these embodiments pertain will appreciate that alterations andchanges in the described structures and methods of operation may bepracticed without meaningfully departing from the principle, and scopeof these embodiments. For example, storing the application fluid in thecoiled tubing in advance of the application may be beneficial incircumstances other than those of large particle size. This may includesituations where the application fluid includes flammables, hazardoussubstances or substances that are naturally damaging to the applicationpump. Also, constituents provided in dissolvable pouches or packets maypose similar challenges and may be well suited for pre-storing in thecoiled tubing. The same may be true where multiple application fluidtypes are to be utilized sequentially or where one is employed totrigger another. For example, two or more different fluids can be loadedinto the coiled tubing one after another. For instance, a first fluidcan precondition the formation to receive a second fluid. Spacers canalso be used between such fluids. Also, in low temperature formationssome diverters (such as PLA based diverters) can take a long time todegrade. An accelerator fluid can be loaded in the coiled tubing eitherbefore, after or both before and after the diverter fluid in the coiledtubing to enhance contact of the accelerator with the diverter after thefluids are placed in the formation. A fluid and a triggering agent forsuch fluid can also be loaded sequentially into the coiled tubing (withor without a spacer fluid). Furthermore, the foregoing descriptionshould not be read as pertaining only to the precise structuresdescribed and shown in the accompanying drawings, but rather should beread as consistent with and as support for the following claims, whichare to have their fullest and fairest scope.

We claim:
 1. A method of delivering an application fluid to a downholelocation in a well from a wellsite, the method comprising: filling thecoiled tubing with the application fluid at a filling pressure with thecoiled tubing positioned at the oilfield surface; and transferring theapplication fluid from the coiled tubing to the downhole location at anapplication pressure that is substantially greater than the fillingpressure.
 2. The method of claim 1 further comprising storing theapplication fluid in the coiled tubing at the wellsite for anoperator-determined period after the filling thereof and prior to thetransferring of the application fluid to the downhole location.
 3. Themethod of claim 1 further comprising increasing pressure in the coiledtubing from the filling pressure to a pre-application pressure that iscloser to the application pressure than the filling pressure in advanceof the transferring of the fluid from the coiled tubing to the downholelocation.
 4. The method of claim 1 wherein the transferring of theapplication fluid from the coiled tubing to the downhole locationcomprises pumping a driving fluid in communication with the coiledtubing at the application pressure to direct the application fluid fromthe coiled tubing to the well.
 5. The method of claim 4 furthercomprising introducing a barrier plug to the application fluid in thecoiled tubing in advance of the pumping of the driving fluid to minimizemixing of the application fluid and the driving fluid.
 6. The method ofclaim 4 wherein the viscosity of the driving fluid is greater than theviscosity of the application fluid to minimize mixing of the applicationfluid and the driving fluid.
 7. The method of claim 4 further comprisingremotely opening a valve for a predetermined period to direct apredetermined amount of the application fluid from the coiled tubing. 8.The method of claim 1 further comprising: deploying the coiled tubing inan interventional downhole application; and retiring the coiled tubingfrom further interventional downhole deployment based on an assessmentof coil life therefor, the deploying of the coiled tubing and theretiring thereof taking place in advance of the filling of the coiledtubing with the application fluid.
 9. A system for positioning at anoilfield, the system comprising: a tubular storage device having asurface to volume ratio of at least about 1, the volume to accommodatean application fluid for use in an application at the oilfield; atransfer pump coupled to the tubular storage device for filling thedevice with the application fluid at a filling pressure; and anapplication pump coupled to the tubular storage device for pressurizingthe filled device to a pressure substantially greater than the fillingpressure.
 10. The system of claim 9 wherein the application fluidincludes at least one constituent having a size of greater than about 4mm.
 11. The system of claim 10 wherein the constituent is selected froma group consisting of a fiber, balls, proppant, projectiles, divertermaterial, a fiber pill, a viscous pill, cement particles and particlesof irregular shape.
 12. The system of claim 9 wherein the fillingpressure is under about 500 PSI.
 13. The system of claim 12 wherein theapplication pump is a triplex pump and the substantially greaterpressure is in excess of about 15,000 PSI.
 14. The system of claim 13wherein the triplex pump accommodates a driving fluid substantially freeof constituents having a size of greater than about 4 mm.
 15. The systemof claim 14 wherein the tubular storage device is coiled tubing.
 16. Thesystem of claim 15 wherein the system further comprises: a support reelto accommodate the coiled tubing in a wound manner thereabout; and aport supported by the reel for controlled fluid communication with thecoiled tubing to allow introduction of a plug barrier between thedriving fluid and the application fluid.
 17. A fluid storage assemblyfor positioning at an oilfield to support a downhole application in awell, the assembly comprising: non-interventional coiled tubing forretaining at the oilfield to supply stored application fluid therein tothe well for the application; and a reel to support the coiled tubingwound thereabout, the reel accommodating a low pressure line coupled tothe coiled tubing for filling with the application fluid at a fillingpressure and accommodating a high pressure line coupled to the coiledtubing for pressurizing the application fluid in the coiled tubing to apressure substantially greater than the filling pressure.
 18. The fluidstorage assembly of claim 17 wherein the non-interventional coiledtubing is of a capacity to store in excess of 30 barrels of theapplication fluid.
 19. The fluid storage assembly of claim 17 whereinthe non-interventional coiled tubing comprises coiled tubing with apredetermined interventional coil life that is retired to anon-interventional status after about 75% of the coil life.
 20. Thefluid storage assembly of claim 17 further comprising containment barslocated about the reel to reinforce the non-interventional coiled tubingduring the pressurizing of the application fluid therein.